1. Field of the Invention
The present invention relates generally to input devices and, more particularly, to improvements for touch panel displays.
2. Background of the Related Art
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as, admissions of prior art.
Input devices perform the function of providing some means for entering commands and data into a computer, data processor, or information system. A variety of input devices are currently available, including keyboards, light pens, data tablets, mice, track balls, joysticks, scanners, voice recognition devices, and touch screens. Each of these input devices exhibits various advantages and disadvantages, and the input device or devices used in any particular application are typically chosen to maximize the efficient input of information into the system.
This disclosure is primarily directed to the last of the input devices mentioned above, namely touch screens. Unlike the other input devices mentioned above, touch screens not only act as a data input device, they also act as a display unit. Essentially, a touch screen is a display unit with some form of a touch-sensitive surface. Due to this unique characteristic, touch screens are currently utilized in a variety of different applications, such as computer terminals, cash registers, automatic teller machines, and automated gasoline pumps to name just a few.
Currently, there are at least four different technologies used for touch screens: (1) capacitive, (2) resistive, (3) surface acoustic wave, and (4) light beam interruption. Although each of these different types of touch screens operate in a different manner and exhibit certain advantages and disadvantages, certain similarities exist. For example, regardless of the type of touch screen, the touch screen system typically includes a sensor unit, which senses the location touched on the display, and a controller unit, which interfaces with the sensor unit and communicates the location information to a system computer. Thus, regardless of the technology employed, each type of touch screen performs the same general function.
However, it is the differences in the way that the various types of touch screens operate that causes a designer to use one type of touch screen over another for a particular application. Resistive touch screens, for example, advantageously exhibit low cost, high touch point density, and can be operated with a gloved hand. Disadvantageously, however, resistive touch screens can be easily damaged and exhibit poor display characteristics (particularly in sunlight). Capacitive touch screens also provide high touch point density and low cost, but capacitive touch screens can be easily damaged, must be calibrated due to large temperature changes, and cannot be operated with a gloved hand.
In contrast, surface acoustic wave touch screens have no overlay to be damaged or to reduce the visual quality of the display. However, surface acoustic wave touch screens typically exhibit the highest cost and can be falsely triggered by noise, wind, transmission signals, and insects. Touch screens that use light beam interruption, typically called infrared touch screens, are relatively expensive. Advantageously however, they have no touch sensitive overlay to be damaged, exhibit high touch point density, can be operated with heavy gloves, exhibit good immunity to most false trigger sources, and are extremely rugged and weather sealable. Although these advantages typically make infrared touch screens the most suitable type of touch screen to use in outdoor applications, high ambient light conditions, such as direct sunlight, can cause an infrared touch screen to malfunction.
It can be seen that each type of touch screen exhibits some disadvantage which makes it not well suited for outdoor use, particularly in high ambient light conditions. Of the different types of touch screens mentioned above, resistive touch screens typically offer the lowest cost along with very good operational performance. In a resistive touch screen, a display, such as a liquid crystal display, resides beneath a multi-layered screen overlay. The top layer touched by a user is a plastic layer with a transparent metallic film on its underside. This top layer is separated by insulating spacers from a bottom layer that has a metallic film on its upper side. These metallic films face one another so that the films make contact when a user presses the top layer into contact with the bottom layer. A conductive path is formed at the point of contact. Thus, the films act as a voltage divider, and the voltage at the point of contact may be measured in the X and Y directions by applying the voltage in one direction and then the other direction. The measured voltages may then be sent to a controller where they are converted into coordinates on the screen and sent to a computer.
This overlay screen suffers in outdoor applications, and particularly in sunlight, for various reasons. First, the typical reflectance of such overlay screens is about 25%, making the underlying display difficult to read. Second, such overlay screens allow most of the infrared radiation from sunlight to be absorbed by the underlying liquid crystal display, and this radiation can cause solar thermal loading of the display which lead to display malfunction. Third, the materials used for such overlay screens tend to deteriorate rapidly from exposure to the ultraviolet rays of the sun. Fourth, the top layer touched by users is easily scratched or damaged, thus requiring the whole touch panel to be replaced.
The present invention may address one or more of the problems set forth above.
Certain aspects commensurate in scope with the originally claimed invention are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below.
In accordance with one aspect of the present invention, there is provided a touch panel display system that includes a computer, a controller coupled to the computer, and a display screen coupled to the computer. A touch panel is coupled to the controller and disposed over the display screen. The touch panel includes a base plate being disposed adjacent the display screen. The base plate has a rigid substrate having an upper surface and a lower surface. A first conductive layer is disposed over the upper surface of the rigid substrate. An anti-reflective dielectric layer is disposed over the first conductive layer, and the anti-reflective dielectric layer has openings through to the first conductive layer. A first anti-reflective layer is disposed on the lower surface of the rigid substrate. A top plate is disposed in spaced apart relation over the base plate. The top plate has a flexible substrate having an upper surface and a lower surface. A hard coating layer and a second anti-reflective layer are disposed over the upper surface of the flexible substrate, and an anti-reflective conductive layer is disposed on the lower surface of the flexible substrate.
In accordance with another aspect of the present invention, there is provided a touch screen overlay that includes a flexible substrate having an upper surface and a lower surface. Double stick adhesive tape is coupled to the lower surface of the flexible substrate.
In accordance with still another aspect of the present invention, there is provided a touch screen that includes a top plate having an upper surface and a lower surface and a base plate having an upper surface and a lower surface. A member detachably couples the lower surface of the top plate to the upper surface of the base plate.
In accordance with yet another aspect of the present invention, there is provided a method of repairing a damaged touch screen having a flexible top plate disposed in spaced apart relation over a relatively rigid base plate. The method includes the acts of: (a) removing the top plate from the base plate; and (b) disposing a replacement top plate on the base plate.
In accordance with a further aspect of the present invention, there is provided a method of manufacturing a touch panel. The method includes the acts of: (a) providing a base plate; (b) providing a top plate; and (c) detachably disposing the top plate over the base plate in spaced apart relation.
In accordance with a still further aspect of the present invention, there is provided a method of manufacturing a touch panel. The method includes the acts of: (a) disposing a layer of conductive material over an upper surface of a relatively rigid substrate of a base plate; (b) disposing a patterned layer of anti-reflective dielectric material over the layer of conductive material, the patterned layer of anti-reflective dielectric material having openings through to the layer of conductive material; (c) disposing a first layer of anti-reflective material over a lower surface of the relatively rigid substrate of the base plate; (d) disposing a second layer of anti-reflective material over an upper surface of a relatively flexible substrate of a top plate; (e) disposing a layer of anti-reflective conductive material over a lower surface of the relatively flexible substrate of the top plate; and (f) arranging the top plate over the base plate such that the anti-reflective conductive material disposed over the lower surface of the top plate is in spaced apart relation to the patterned anti-reflective dielectric layer disposed over the upper surface of the base plate.
In accordance with a yet further aspect of the present invention, there is provided a sensing unit for a touch panel. A first plate of the touch panel has a first layer of conductive material disposed on its surface. A second plate of the touch panel has a second layer of conductive material disposed on its surface and has a layer of dielectric material disposed over the second layer of conductive material such that a peripheral portion of the second layer of conductive material remains exposed. The layer of dielectric material has openings through to the second layer of conductive material. A substantially continuous resistive member is disposed over the exposed peripheral portion of the second layer of conductive material adjacent a periphery of the layer of dielectric material. A plurality of conductive traces is disposed on the layer of dielectric material, where each of the plurality of conductive traces has a first end coupled to a respective selected location of the resistive member.